Hearing loss that is a hearing impairment is divided into conductive hearing loss and sensorineural hearing loss. The conductive hearing loss is caused due to a disorder of an outer ear or a middle ear in sound conduction. The sensorineural hearing loss is caused mostly due to a disorder of an inner ear. While improvements through surgery can be expected in the conductive hearing loss, an auxiliary auditory device such as a hearing aid or a cochlear implant is necessary for compensation of the sensorineural hearing loss.
Serious sensorineural hearing loss cannot be compensated sufficiently even with the hearing aid. To tackle this problem, a cochlear implant as disclosed in Non-patent Literature 1 has been proposed for remedy for serious sensorineural hearing loss.
The cochlear implant directly applies electric stimuli to an auditory nerve using a multichannel electrode embedded in a cochlea to cause the brain to recognize the sounds. The use of the cochlear implant can recover the auditory sense of a patient whose inner ear is impaired.